Project III-The Roles of N-glycans in Carbohydrate-Mediated Cell Adhesion (Michiko N. Fukuda, Ph.D.) Alpha-mannosidase IIx(MX) is an enzyme closely related to the Golgi processing alpha-mannosidase II (MII). To investigate the in vivo role of MX, we generated MX-deficient ,mutant mice, and found that MX null mice were born and grew normally but MX null males are sterile due to ineffective spermatogenesis. Our previous studies on HEMPAS disease and evidence derived from the MII gene knock-out mouse suggested the existence of an enzyme potentially compensating for the MII defect. In order to determine if MX and MII compensate for each other's loss in vivo, we produced MII/MX double gene knock-out mice. MII/MX double null mutants are embryonic lethals, indicating that MX and MII together are essential for N-glycan processing. Using these mutant mice, we will define the roles of MX in N-glycan biosynthesis. By generating conditional MII/MX double null mutants, we will determine the contribution of N-glycans to E- and P-selectin in neutrophils and T helper 1 cells. In addition, because we have identified in sulfotransferase responsible for MCD (macular corneal dystrophy), whose product is structurally similar to the L-selectin ligand, we will also determine if this sulfotransferase is involved in the synthesis of L-selectin ligand, we will also determine if this sulfotransferase is involved in the synthesis of L- selectin ligand in vivo in the mouse. Specific aims are to (1) determine the role of MX in N-glycan in vivo in the mouse. Specific aims are to (1) determine the role of MX in N-glycan biosynthesis, (b) to determine the contribution of N-glycans to the ligand activities of E- and P-selectin, and (3) to determine if mouse I-GlcNAc6ST, a sulfotransferase which also functions as keratan sulfate GlcNAc6ST, is involved in sulfation of L-selectin ligand in the mouse.